Transmitting and receiving device for optical cable and alignment method thereof

ABSTRACT

Embodiments according to the present disclosure relate to an optical transmitting device and an optical receiving device which can minimize the alignment error between the light source and the photodetector on the substrate, miniaturize the devices, and require no separate guide member reducing manufacturing costs, while satisfying the design requirements for sub-miniaturization, and performing optical transmission and reception more efficiently.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of International ApplicationNo. PCT/KR2016/014737, filed Dec. 15, 2016, which is based upon andclaims the benefit of priorities from Korean Patent Application Nos.10-2015-0179014 and 10-2015-0179030, both filed on Dec. 15, 2015. Thedisclosures of the above-listed applications are hereby incorporated byreference herein in their entireties.

BACKGROUND OF THE INVENTION Technical Field

The present disclosure in some embodiments relates to an opticaltransmitting device and an optical receiving device for an optical fibercable and a method of aligning thereof.

Discussion

The statements in this section merely provide background informationrelated to the present disclosure and do not necessarily constituteprior art.

Optical fiber-based signal transmission methods, which are in extensiveuse for a long haul communication, have widespread applications in alarge-capacity digital media transmission including a high-definitiondigital video display for which high-speed and high-density datatransmission is required, owing to the operation characteristicsunaffected by an electromagnetic interference (EMI) and usefulness in abroad bandwidth of the optical fiber.

These optical fiber-based signal transmission methods can be implementedby arranging a lens and a reflector configured between an optical fiberand an optical element. One possible way to achieve such configurationis to install the optical fiber and a structure affixed with thereflector and the lens on a substrate mounted with the optical elementto establish an optical alignment.

This method of optical alignment can be incorporated into manufacturingan optical transceiver, where a selected way of aligning the opticalelement, the lens, the reflector and the optical fiber dictates thestructural simplification, manufacturing cost reduction, and durabilityand precision enhancements, etc., which exhibits the paramountsignificance of the optical alignment issue.

However, an optical transceiver manufactured by the optical alignment ofthe conventional method is not only highly costly but also too bulky tofit in a mobile communication device such as a smartphone, and istroubled with instability issues due to a complicated structure.

Korean Patent Application No. 2014-0168272 filed on Nov. 28, 2014 bythis applicant proposed an apparatus for optical transmitting andreceiving as shown in FIGS. 1A and 1B.

The apparatus for optical transmitting and receiving or opticaltransmitting and receiving device includes a baseplate 1210′ and anoptical-fiber fixing block 1300′. The baseplate 1210′ includes a setposition for mounting an optical element 1215′, a first reference holeA′, and a second reference hole B′ spaced by a first distance from thefirst reference hole A′. The optical-fiber fixing block 1300′ isconfigured to fixedly mount at least one of a lens unit 1320′ and anoptical fiber 1340′ optically linked with the optical element 1215′, andit includes a first post C′ configured to be inserted into the firstreference hole A′ and a second post D′ configured to be inserted intothe second reference hole B′.

The optical fiber 1340′ is inserted along guide surfaces 1310′. Theoptical element 1215′ and the lens unit 1320′ are arranged so that theircenters are vertically aligned, and a reflector 1330′ is installed onthe upper part of the lens unit 1320′. Light emitted from the opticalfiber 1340′ is deflected via the reflector 1330′, focused via the lensunit 1320′ and thereby made incident on the optical element 1215′.Conversely, light emitted from the optical element 1215′ is focused viathe lens unit 1320′ and deflected via the reflector 1330′ such that thelight is incident on the optical fiber 1340′.

Such an optical transmitting and receiving device exhibits excellentefficiency serving the two individual purposes oftransmission/reception, but has the following drawbacks.

Recent embedded system specifications require that the overall height ofthe optical transmitting and receiving device be 1 mm or less to fit thestandard IC package. The main issue in designing and manufacturing inaccordance with this requirement is that reducing the diameter orthickness of the lens unit has its light concentration ratio droppedcorrespondingly to inhibit a designed performance of the opticaltransmission and reception. In addition, reducing the external dimensionof the device with the size of the lens unit maintained causes anoptical loss at the reflector and an increased refraction angle of thelight incident on the optical fiber to inhibit a part of the light frombeing guided through the optical fiber, resulting in structuralmisalignment of the optical system.

Here, the present inventors have determined that there is a limit tofulfilling a new specification with an existing device that performsboth transmission and reception of light, and found that an opticaltransmitting device dedicated advantageously to optical transmissionscan satisfy design requirements for sub-miniaturization as well astransmit light more efficiently.

At the same time, the present inventors have found an improved method ofaligning the lens of the optical transmitting device and the lightsource on a substrate.

SUMMARY OF THE INVENTION

The following description of some embodiments of the present disclosureis based on these findings.

Therefore, the first and second embodiments of the present disclosureseek to provide an optical transmitting device and an optical receivingdevice respectively suitable for the design requirements forsub-miniaturization.

The first and second embodiments provide new types of opticaltransmitting and receiving devices to reduce the tolerance as well asthe size of the devices which are economical, convenient to manufactureand so on.

The first and second embodiments further seek to provide aligningmethods capable of limiting the alignment error between the opticaltransmitting and receiving devices and the substrates to within a fewmicrometers and minimizing the error.

Technical problems to be solved by the present disclosure are notlimited to the above, but other unmentioned technical problems resolvedwill be clearly understood by a person of ordinary skill in thepertinent art from the description below.

According to one aspect of the first embodiment of the presentdisclosure, an optical transmitting device is provided including a firstlens, a reflector disposed above and in alignment with the first lens, asecond lens disposed on a side of and in alignment with the reflector soas to receive light reflected by the reflector, and a housing configuredto house the first lens, the second lens, and the reflector. Here, thehousing has a divided structure composed of a body at a lower positionand a cover at an upper position, and the housing has a height less than1 mm.

According to another aspect of the first embodiment, a method ofaligning the optical transmitting device is provided including providinga substrate coupled to the optical transmitting device and including alight source, and coupling a first post to a first reference holeprovided in the substrate, and coupling a second post to a secondreference hole provided in the substrate, and aligning a first lensprovided in the optical transmitting device with the light source of thesubstrate.

According to one aspect of the second embodiment, an optical receivingdevice.

The optical receiving device includes a focusing lens, a reflectordisposed above and in alignment with the focusing lens, and a housingconfigured to house the focusing lens and the reflector. Here, thehousing has a height less than 1 mm, and the housing has a bottomprovided with a first post and a second post extending downward atpredetermined front and rear positions of the bottom, respectively.

According to another aspect of the second embodiment, a method ofaligning an optical receiving device is provided, including providing asubstrate coupled to the optical receiving device and including aphotodetector, and coupling a first post to a first reference holeprovided in the substrate, and coupling a second post to a secondreference hole provided in the substrate, and aligning a focusing lensprovided in the optical receiving device with the photodetector of thesubstrate.

According to yet another embodiment of the present disclosure, anoptical transmitting device includes a body and a cover. The bodyincludes a first lens configured to modify a diverging beam of lightemitted from a light source into a parallel beam of light, and areflector arranged above the first lens and configured to reflect lightfrom the first lens. The cover is configured to be coupled with the bodyto form a housing and it includes a second lens configured to collectthe light from the reflector and transmit the light to an optical fiber,and an optical fiber guide unit configured to guide the optical fiber.Here, the second lens is installed at a predetermined position to fullyaccommodate the light reflected by the reflector and to establish aseamless optical path running from the light source through the firstlens, the reflector and the second lens to the optical fiber.

According to yet another embodiment of the present disclosure, anoptical communication assembly includes a body, a cover and a substrate.The body includes a collimating lens configured to modify a divergingbeam of light emitted from a light source into a parallel beam of light,and a reflector arranged above the collimating lens and configured toreflect light from the collimating lens. The cover is configured to becoupled with the body to form a housing and it includes a focusing lensconfigured to collect the light from the reflector and transmit thelight to an optical fiber, and an optical fiber guide unit configured toguide the optical fiber. The substrate is configured to be coupled tothe light source and the body. Here, the focusing lens is installed at apredetermined position to fully accommodate the light reflected by thereflector and to establish a seamless optical path running from thelight source through the collimating lens, the reflector and thefocusing lens to the optical fiber. The body comprises a first post anda second post installed extending downward at predetermined front andrear positions in a bottom of the body. The substrate comprises a firstreference hole and a second reference hole configured to be coupled withthe first post and the second post, respectively.

According to the first embodiment, by utilizing a lens group including aplurality of lenses, an optical transmitter is provided that canfunction as an optical transmitting device while satisfying the designrequirements for sub-miniaturization, and can perform opticaltransmission more efficiently.

According to the second embodiment, an optical receiving device isprovided that can function as an optical receiver while satisfying thedesign requirements for sub-miniaturization, and can perform opticalreception more efficiently.

Further, the optical transmitting device according to the presentalignment method minimizes the alignment error with a light source onthe substrate, provides for the miniaturization thereof, and obviatesthe need for a separate guide member so as to reduce the manufacturingcost of the device.

Further, the optical receiving device according to the present alignmentmethod minimizes the alignment error with a photodetector on thesubstrate, provides for the miniaturization thereof, and obviates theneed for a separate guide member so as to reduce the manufacturing costof the device.

Besides, different embodiments of the present disclosure exhibit avariety of corresponding effects such as the devices with excellentdurability, which will be clearly illustrated by the embodimentsdescribed below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view of a conventional apparatus fortransmitting and receiving light.

FIG. 1B is a side view of FIG. 1A.

FIG. 2 is a conceptual diagram for illustrating the principle of opticaltransmission of an optical transmitting device according to a firstembodiment.

FIG. 3 is a perspective view of the overall appearance of the opticaltransmitting device of the first embodiment.

FIGS. 4A and 4B are a left side view and a plan view of the body of theoptical transmitting device of the first embodiment.

FIGS. 5A and 5B are a left side view and a plan view of a cover of theoptical transmitting device of the first embodiment.

FIGS. 6A and 6B are a left side view and a plan view illustrating that ahousing made of the body and the cover of the first embodiment iscoupled with a substrate.

FIGS. 7A to 7C are conceptual diagrams illustrating a method of aligningthe optical transmitting device according to the first embodiment on asubstrate, of which FIG. 7B is a diagram of the principle of the methodwhere a first post is fixed, and FIG. 7C is a diagram of the principleof the method illustrating a second post is fixed.

FIG. 8 is a conceptual diagram illustrating the principle of opticalreception of the optical receiving device according to the secondembodiment.

FIG. 9 is a perspective view of the overall appearance of the opticalreceiving device of the second embodiment.

FIGS. 10A and 10B are a left side view and a plan view of the opticalreceiving device of the second embodiment.

FIG. 11 is a left side view illustrating that the housing of the secondembodiment is coupled to the substrate.

FIGS. 12A to 12C are conceptual diagrams illustrating a method ofaligning the optical receiving device according to the second embodimenton a substrate, of which FIG. 12B is a diagram of the principle of themethod where the first post is fixed, and FIG. 12C is a diagram of theprinciple of the method illustrating a second post is fixed.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, some embodiments of the present disclosure will bedescribed in detail with reference to the accompanying drawings. In thefollowing description, like reference numerals designate like elements,although the elements are shown in different drawings. Further, in thefollowing description of the at least one embodiment, a detaileddescription of known functions and configurations incorporated hereinwill be omitted for the purpose of clarity and for brevity.

Additionally, various terms such as first, second, A, B, (a), (b), etc.,are used solely for the purpose of differentiating one component fromthe other but not to imply or suggest the substances, the order orsequence of the components. Throughout this specification, when a part“includes” or “comprises” a component, the part is meant to furtherinclude other components, not excluding thereof unless specificallystated to the contrary.

If any component is described as ‘connected’, ‘coupled’ or ‘fastened’ toanother component, the components are not only meant to be directly‘connected’, ‘coupled’, or ‘fastened’ but also are indirectly‘connected’, ‘coupled’, or ‘fastened’ via one or more additionalcomponents.

In addition, the size, shape, etc. of the components illustrated in thedrawings can be exaggerated for clarity of explanation and convenience.The terms specifically defined in consideration of the configuration andoperation of the present disclosure are only for explaining someembodiments of the present disclosure and are not intended to limit thescope of the present disclosure.

The transmission/reception apparatus for an optical fiber cable,according to some embodiments of the present disclosure may bemanufactured as two different modules. One module is a transmittingdevice that performs an electric-optical signal conversion and transmitsthe converted optical signal via an external optical fiber cable. Theother module is a receiving device that receives an optical signal viaan external optical fiber cable and performs an optical-electric signalconversion. A transmitting device for an optical fiber cable accordingto at least one embodiment of the present disclosure will be describedin the first embodiment, and a receiving device for an optical fibercable will be described in a second embodiment.

Hereinafter, the principle, structure and then alignment method of anoptical transmitting device 1 presented as the first embodiment of thepresent disclosure will be explained.

1. Principle of Optical Transmission

First, referring to FIG. 2, the principle of optical transmission willbe described concentrating on the optical structure of the opticaltransmitting device 1 of the first embodiment of the present disclosure.

The optical transmitting device 1 faces a substrate 10 installed with alight source 12 as an optical element, and includes a lens group 20, areflector 14 and an optical cable 30. The lens group 20 has a first lens22 installed between the light source 12 and the reflector 14, and asecond lens 24 installed between the reflector 14 and the optical cable.An optical fiber 32 is inserted in the optical cable 30. The reflector14 includes, but is not limited to, a prism.

The light source 12, the first lens 22 and the reflector 14 are alignedso that the centers of the three members are aligned in the verticaldirection. Likewise, the reflector 14, the second lens 24 and theoptical cable 30 are laterally aligned so that the centers of thereflector 14 and the second lens 24 coincide with the center point ofthe light receiving portion of the optical cable 30. Methods foraligning the light source 12 and the first lens 22 are disclosed inapplicant's earlier Korean Patent Application Nos. 2014-0168272 and2013-0146599, which are hereby incorporated by reference into thecontents of this application.

The first lens 22 is preferably a collimating lens and the second lens24 is preferably a focusing lens. Light that has passed through acollimating lens becomes collimated light, and light that has passedthrough a focusing lens is focused. Therefore, as shown in the drawing,the light emitted from the light source 12 is collimated by passingthrough the first lens 22, propagates towards the reflector 14, isreflected by the reflector 14, travels towards and passes through thesecond lens 24, and then coupled into the core of the optical fiber 32where the light is focused.

Multiples of the light source 12 may be aligned in a row on thesubstrate. In this case, multiple first lenses 22 and second lenses 24are installed in a row in alignment with the respective light sources12.

The adoption of the lens group 20 including the plurality of lenses ofthe first lens 22 and the second lens 24 is a feature of some embodimentof the present disclosure. Maintaining a single-lens structure with onlya focusing lens displaced between a light source and a reflector whilemeeting the design requirement for sub-miniaturization of asubmillimeter height limit leads to a reduced size of the lens and ashortened optical path, particularly where light needs to propagatethrough its micro heights. Thereby, the light emitted from the lightsource fails to gather accurately on the reflector, and part of thelight reflected by the reflector is incident on the optical fiber at anangle with the fiber axis exceeding the fiber's total reflectioncritical angle to disable its propagation through the optical fiber,resulting in an optical loss with the light scattering outside the fibercladding. To the contrary, with the adoption of the lens group 20 madeof the plurality of lenses including the first lens 22 and the secondlens 24, the optical transmitting device 1 of some embodiments of thepresent disclosure functions exclusively as an optical transmitterdifferent from the conventional optical apparatus for both transmissionand reception operations. At the same time, the optical transmittingdevice 1 satisfies the design requirements for sub-miniaturization, andperforms optical transmission more efficiently.

The main function of the first lens 22 is to reduce the beam divergenceof light emitted from the light source 12, to alleviate the burden ofthe second lens 24 with the duty to focus the light and at the same timeto increase the optical alignment tolerance. The distributed dutiesbetween the lens with respect to the coupling of the optical signalreduces the influence of the numerical aperture (NA) which is aconstraint of the optical waveguide of the optical fiber. This meansthat the refractivity of the lens can be adjusted according to thedivergence of the light. In particular, using the second lens 24 tofocus the collimated beam of light from the first lens 22 facilitates tomaximally focus the light into the optical fiber that has apredetermined NA.

2. Structure of Optical Transmitting Device

FIG. 3 is a perspective view of the overall appearance of the opticaltransmitting device 1 including the structure of FIG. 2 of the presentdisclosure.

The optical transmitting device 1 includes a housing 2 in which the lensgroup 20 and the reflector 14 are installed. The optical transmittingdevice 1 is coupled face-to-face to the substrate 10 on which the lightsource 12 is installed.

The housing 2 is approximately quadrangular and has a divided structureof a body 3 and a cover 4. The cover 4 has its upper surface providedwith a hole 40 for injecting an adhesive such as epoxy, and has at itsrear a trapezoidal cut to provide a guide 41 for the optical cable 30.

The height (H) of the housing 2 is on a sub-millimeter, orsub-miniature, scale. This is a smaller thickness than a typicalelectronic chip, and the optical transmitting device 1 of someembodiments of the present disclosure is useful for application todevices with small thickness or small form factor.

The optical transmitting device 1 of some embodiments has a moldedarticle for optical alignment removed, and it is suffice to perform theoptical alignment with the housing 2 and the substrate 10 themselves andthereby reduces the alignment error generated by using the moldedarticle. The housing 2 is manufactured by plastic injection molding tofacilitate mass production and assembly thereof.

FIGS. 4A and 4B are a left side view and a plan view of the body 3 ofthe optical transmitting device 1.

The body 3 has a bottom 300 of a long rectangle, a left side couplingportion 310 and a right side coupling portion 312, each having a heightlarger than the bottom 300 and extending from near the front of the tipof the bottom 300 to near a middle region thereof. The bottom 300 iscentrally positioned and enclosed by the left coupling portion 310 andthe right coupling portion 312 from both sides. Starting from the frontto the rear, the left coupling portion 310 includes a first flap 315projecting upward, a first receiving hole 313 and a first latch member316 projecting upward. Likewise, the right coupling portion 312 includesa second flap 317, a second receiving hole 314 and a second latch member318 projecting upward. Generally, the left coupling portion 310 and theright coupling portion 312 are symmetrical structures of the same shape.

The first flap 315 and the second flap 317 extend vertically upward fromthe bottom 300, and protect the first lens 24 and the reflector 14 fromthe left and right, respectively. The latch members 316, 318 and thereceiving holes 313, 314 are members to be coupled with correspondingelements of the cover 4. In this arrangement, the left coupling portion310 and the right coupling portion 312 provide a protective frame forthe lens and the reflector and provide a fastening structure forcooperating with the cover 4. Therefore, as long as their functions areoffered, the above members may have their size, shape and positionarbitrarily changed.

The bottom 300 and the coupling portions 310, 312 may be integrated withone another, although their formation is not necessarily limitedthereto.

The bottom 300 has an open space 300S behind the left and right couplingportions 310, 312, which cooperates with the cover 4 so as to provide aspace through which the optical fiber passes. This optical fiber spaceis closed by the cover 4 at its third flap 403 and fourth flap 408described below to provide an optical fiber guiding structure which isimpervious to external impacts and vibrations.

The bottom 300 is formed with a first post 302 and a second post 303 inpredetermined positions forward and rearward respectively along thelongitudinal center line thereof, which extend downward toward thesubstrate. The first post 302 and the second post 303 are circularcolumns protruding downward. In the example shown in FIG. 4A, in orderto tolerate the error of optical alignment, the first post 302 is atapered column having its diameter gradually reduced downward by minutedegrees, and the second post 303 is a straight column having a constantdiameter. The diameter of the first post 302 is larger than that of thesecond post 303 in the vicinity of the top of the first post 302, thatis, adjacent to the bottom 300. This means that with respect to thesecond post 303, the diameter of the first post 302 may be larger on itsupper side of a reference point in the vertical direction and smaller onits lower side of the reference point.

Then, the body 3 of some embodiments of the present disclosure utilizesa reflector mount 301 and a first lens mount 304 for installing thereflector 14 and the first lens 22, respectively. As shown in FIG. 4A,the reflector mount 301 rises vertically from the tip of the bottom 300.The first lens mount 304 is spaced apart from the reflector mount 301 bya predetermined distance and is formed in front of the reflector mount301, and it extends from a lower end portion of the bottom 300 to aheight slightly higher than the start point of the reflector mount 301until it is redirected to extend forward laterally to generally form aninverted L-shape. The reflector mount 301 and the first lens mount 304may be made to be integrated with the bottom 300 or they may beseparately manufactured in a unitized module and coupled to the bottom300.

The first lens 22 is installed on an upper surface 304 a of the firstlens mount 304 with its convex surface facing downward. The reflector 14is obliquely installed across the end of the upper surface 304 a and theapex of the reflector mount 301. When multiples of the first lens 22 areinstalled, as shown in FIG. 4B, the first lenses 22 are installed in arow along the upper surface 304 a with a certain interval therebetween.In this case, the reflector 14 may be a single prism installed forproviding a constant reflecting surface.

As long as the reflector mount 301 and the first lens mount 304 performthe optical transmission function described with reference to FIG. 2 andserve to house the first lens 22 and the reflector 14 so as to providean optical path suitable for the optical transmitting device 1 of someembodiments of the present disclosure, they may be freely modified inshape, size and position.

As described above, the present disclosure in some embodiments adopts adivided structure wherein the first lens 22 and the reflector 14 areinstalled in the body 3, and the second lens 24 is installed in thecover 4, which facilitates designing and manufacturing of a suitablecompact optical transmitting device for sub-miniaturizationrequirements.

FIGS. 5A and 5B are a left side view and a plan view of the cover 4 ofthe optical transmitting device 1.

The cover 4 has an elongated rectangular shape and includes an upperside 400 wider than the bottom 300. On the lower part of the upper side400, a left coupling portion 420 is formed to correspond to the leftside contour of the body 3 and a right coupling portion 430 is formed tocorrespond to the right side contour of the body 3. Starting from thefront to the rear, the left coupling portion 420 includes a third latchmember 401 projecting downward, a third receiving hole 402, and a thirdflap 403 projecting downward. Similarly, the right coupling portion 430includes a fourth latch member 406 projecting downward, a fourthreceiving hole 407, and a fourth flap 408 projecting downward from thefront.

As long as the left coupling portion 420 and the right coupling portion430 serve the purpose of providing a protection frame of the opticalfiber cable and fastening with corresponding elements of the body 3,they may be arbitrarily modified in size, shape and position. In someembodiments, the upper side 400 and these coupling portions 420, 430 areintegrated, but are not necessarily limited thereto.

As described above, the upper side 400 is provided with the hole 40 forinjecting an adhesive such as epoxy at the midpoint in the widthdirection in front of the upper side 400. The epoxy resin injectedthrough the hole 40 securely binds the optical fiber and the cover 4together, fills the gap between the wall surface of the second lens 24and the optical fiber end in the coupling process, so as to reduce thereflection that may occur from the surface through which the light istransmitted. Some embodiments of the present disclosure inject, inaddition to epoxy, other highly viscous materials enabling opticalcommunication in cooperation with optical fibers and plastic moldedparts. For example, as a replacement or addition to the epoxy,refractive index matching oil may be injected to desirably reduce the NAof the light incident on the optical fiber.

In some embodiments of the present disclosure, the cover 4 utilizes asecond lens mount 404 for mounting the second lens 24. The second lensmount 404 extends vertically downward from the front portion of theupper surface 300, as shown in FIG. 5A. The second lens 24 is installedon a front surface 404 a of the second lens mount 404. The second lens24 is installed at an elevation set according to the position of thereflector 14 so as to fully accommodate the light reflected by thereflector 14. When there are multiples of the first lens 22, as shown inFIG. 5B, the matching number of second lenses 24 are installed.

The portion where the second lens 24 and the second lens mount 404 areinstalled remains in the cover 4 as an open space 40S which, however, islaterally closed by the first flap 315 and the second flap 317 toprovide a structure of the lens system which is impervious to externalimpact and vibration.

As long as the second lens mount 404 serves its purpose of housing thesecond lens 24 described with reference to FIG. 2 so as to provide anoptical path suitable for the optical transmitting device 1 of someembodiments of the present disclosure, it may be freely modified inshape, size and position.

As described above, the present disclosure in some embodiments adopts adivided structure between the body 3 and the cover 4, which facilitatesdesigning and manufacturing of a suitable compact optical transmittingdevice for sub-miniaturization requirements.

In addition, relocating the second lens 24 installed on the cover 4alone without adjustment of the body 3 may adjust the distance to theoptical fiber or provide an alignment with the path of the reflectedlight from the reflector 14, which facilitates the operation of opticalalignment and calibration.

FIGS. 6A and 6B are a left side view and a plan view illustrating thatthe housing 2 made of the body 3 and the cover 4 described above iscoupled with the substrate 10. For convenience of explanation, FIG. 6Apresents a reference numeral of each left side member, accompanied byits right side counterpart in parentheses.

The first flap 315 and the second flap 317 of the body 3 are fastened tothe cover 4 so as to be in contact with the upper side 400 of the cover4, to provide a protective frame for laterally protecting the opticalsystem including the first lens 22, the reflector 14 and the second lens24.

In the first receiving hole 313 and the second receiving hole 314 of thebody 3, the third latch member 401 and the fourth latch member 406 ofthe cover 4 are accommodated, respectively. Additionally, in the thirdreceiving hole 402 and the fourth receiving hole 407 of the cover 4, thefirst latch member 316 and the second latch member 318 of the body 3 areaccommodated, respectively. Repetitive fastening of these continuousconcavo-convex structures provides secure and accurate fastening of thebody 3 and the cover 4, and it can minimize misalignment after assembly.

Further, the third flap 403 and the fourth flap 408 of the cover 4 arecoupled with the body 3 abutting against the bottom 300 while closingthe space 300 s thereof so as to provide an optical fiber guidingstructure which is impervious to external impacts or vibrations.

One of the structural features of the housing 2 of the opticaltransmitting device of some embodiments is that the body 3 is providedwith the first lens 22 and the reflector 14 and the cover 4 has thesecond lens 24 and the optical fiber guide unit installed therein. Thus,while maintaining this feature, the present disclosure is capable ofvarious modifications at the level of those skilled in the art,including, for example, providing the first flap and the second flap onthe cover 4 with the third flap and the fourth flap provided on the body3, or inversely forming the latch members and the receiving holesbetween the body 3 and the cover 4, or switching the order of formingthe latch members and the receiving holes.

Further, although the explanation has been made on the premise that thelight source 12 is arranged outside the first post 302 and the secondpost 303, the light source 12 when relocated halfway between the firstpost 302 and the second post 303 as disclosed in Korean PatentApplication No. 2014-0168272 may be accommodated by the presentdisclosure with an appropriate adaptation of the housing structure.

Referring again to FIGS. 6A and 6B, the housing 2 of the presentdisclosure is coupled to the substrate 10.

The substrate 10 is formed with a first reference hole 302 a and asecond reference hole 303 a for accommodating the first post 302 and thesecond post 303 of the housing 2. The first post 302 and the second post303 are inserted into the first reference hole 302 a and the secondreference hole 303 a, respectively. The first post 302 which is thetapered column is initially inserted into the first reference hole 302 awith a minute clearance remaining therebetween. As the insertionprogresses gradually, the first post 302 is fixed in a position where itcomes into contact with the first reference hole 302 a without gaps.

As described later, the optical transmitting device 1 of someembodiments having such coupling structure can minimize a misalignmentthat may occur in the process of assembling with the substrate 10.

3. Alignment Method of Optical Transmission Device

The principle of the alignment method of the optical transmitting deviceof the present disclosure will be described with reference to FIGS. 7Ato 7C, which mainly shows the plan view of the substrate 10.

With respect to the light source 12 provided on the substrate 10, thefirst reference hole 302 a and the second reference hole 303 a areformed in a line. The light source 12, first reference hole 302 a andsecond reference hole 303 a respectively have center lines 111, 112 and113 in the widthwise direction (vertical direction in the drawing), andthe light source 12, first reference hole 302 a and second referencehole 303 a have a longitudinal (horizontal direction in the drawing)center line as indicated by 114. “A” is the gap between center line 111and center line 112, and “B” is the spacing between center line 112 andcenter line 113.

In the small form factor optical transmitting device 1 with a height ofless than 1 mm, correction of assembling tolerance means eliminatingerrors of several micrometers, so a sophisticated aligning operation isrequired. Typically, the substrate 10 is completed and supplied inadvance according to specifications. The principal interest in theassembly of the substrate 10 and the optical transmitting device 1 isthe alignment of the first lens 22 with the least possible deviationwith respect to the light source 12 located on the substrate 10. Theideal assembly for this purpose provides a perfect alignment of thecenters of the respective reference holes with the centers of therespective posts free of deviation of even several μm. However, it isdifficult to make a complete intermeshing of members in the actualassembly process. A solution to this problem is to minimize the error byhaving either one of the first post 302 and the second post 303 fixed toeliminate the tolerance issue, and having the tolerance of the otherpost to exclusively affect the position of the first lens 22 to bealigned with the light source 12.

FIG. 7B is a diagram of the principle of the method where the first post302 is fixed immovably. It is assumed that A:B=1:8 and the second post303 is located deflected upward by 20 μm from the center of the secondreference hole 303 a. In this case, the first lens 22 is deviated fromthe light source 12 downwardly by 2.5 μm by proportional expression.

FIG. 7C is a diagram of the principle of the method illustrating thesecond post 303 is fixed immovably. It is assumed that A:B=1:8 and thefirst post 302 is located deflected upward by 20 μm from the center ofthe first reference hole 302 a. In this case, the first lens 22 isdeviated from the light source 12 upwardly by 22.5 μm by proportionalexpression.

Therefore, when the light source 12 is arranged outside with respect toall the reference holes, fixing the first post 302 in proximity to thelight source 12 can eventually reduce the nine-fold error than when thesecond post 303 is fixed. The above principle is applied not only to thecase where the post deviates to the upward direction from the center ofthe reference hole but also to the case where the post deviates in thedownward or left/right direction.

Those skilled in the art will appreciate that assembly errors can beminimized as the proportional relationship of A:B increases, that is, asthe distance between posts increases or the first post is closer to thelight source or the first lens.

In order to fix the first post 302 to the first reference hole 302 a,the optical transmitting device 1 of some embodiments of the presentdisclosure has the first post 302 designed as a tapered column so thatit is inserted into the first reference hole 302 a initially with minutedegrees of clearance provided, and as the insertion graduallyprogresses, the first post 302 is fixed at a position where it is incontact with the first reference hole 302 a without gaps.

The fixed position may be a point where the diameters of the first post302 and the first reference hole 302 a coincide. However, since the postis molded with, for example, a plastic material, it has a property that,when depressed, it is inserted by being compressed and deformed, andwhen pressure is released, returns to the original shape by elasticrestoring force. Therefore, the fixed position may be a position wherethe diameter of the first post 302 is slightly larger than that of thefirst reference hole 302 a, which is a margin for facilitating thefixation of the first post 302.

From the above, one can see that it is desirable to design the firstpost 302 as a tapered column having its diameter continuously increasedfrom a range larger than the diameter of the first reference hole 302 ato a range smaller than the same.

When the position of the first post 302 is fixed, only the position ofthe second post 303 affects the alignment of the light source and thelens, but the latter effect is very small compared to the effect on thelens by the deviation of either the first post 302 or both posts 302,303 from the centers of all the reference holes. Therefore, it becomespossible to restrict the alignment error of the light source and thelens to within a few micrometres to minimize it.

The following describes the principle, structure and then the alignmentmethod of an optical receiving device 1′ presented as the secondembodiment of the present disclosure.

1. Principle of Optical Reception

Referring first to FIG. 8, the principle of optical reception will bedescribed concentrating on the optical structure of the opticalreceiving device 1′ of the second embodiment of the present disclosure.

The light receiving device 1′ according to some embodiments of thepresent disclosure faces a substrate 10 installed with a photodetector12′ as an optical receiving element, and includes a lens 20′, areflector 14′ and an optical cable 30′. The lens 20′ is provided betweenthe photodetector 12′ and the reflector 14′. An optical fiber 32′ isinserted in the optical cable 30′. The reflector 14′ includes, but isnot limited to, a prism.

The photodetector 12′, lens 20′ and reflector 14′ are aligned so thatthe centers of the three members are at the same elevation. Likewise,the reflector 14′ and the optical cable 30 are laterally aligned so thatboth members are aligned such that the reflector 14′ coincide with thecenter point of the light transmitting portion of the optical cable 30′.

The lens 20′ is preferably a focusing lens. The light having passedthrough the focusing lens is focused. Therefore, as shown in thedrawing, the light emitted from the optical fiber 32′ is incident on thereflector 14′, is reflected by the reflector 14′ at right angle, travelsdownward in the drawing and passes through the lens 20′ where the lightis focused and then incident on the photodetector 12′.

Multiples of the photodetector 12′ may be aligned in a row on thesubstrate. In this case, multiple lenses 20′ are installed in a row inalignment with the respective photodetectors 12′.

It is very difficult to design an optical transceiver that performs bothoptical transmission and optical reception while satisfying the designrequirements for sub-miniaturization of a submillimeter height limit.However, it has been found that the single-lens structure with the lenssize reduced for use as an optical receiving device exhibits anexcellent optical receiving efficiency over prior art. On the otherhand, the optical transmitting device needs to adopt a lens group fortransmitting light by focusing the same to the optical fiber at theprecise point.

2. Structure of Optical Receiving Device

FIG. 9 is a perspective view of the overall appearance of the opticalreceiving device 1′ including the structure of the optical receivingdevice of FIG. 8 according to some embodiments.

The optical receiving device 1′ includes a housing 2′ in which a lens20′ and a reflector 14′ are installed. The optical receiving device 1′is coupled face-to-face to the substrate 10′ on which the photodetector12′ is installed.

The height (H) of the housing 2′ is on a sub-millimeter, orsub-miniature, scale. This is a smaller thickness than a typicalelectronic chip, and the optical receiving device 1′ of some embodimentsof the present disclosure is useful for application to devices withsmall thickness or small form factor.

The optical receiving device 1′ of some embodiments has a molded articlefor optical alignment removed, and it is suffice to perform the opticalalignment with the housing 2′ and the substrate 10′ themselves andthereby reduces the alignment error generated by using the moldedarticle. The housing 2′ is manufactured by plastic injection molding tofacilitate mass production and assembly thereof.

The housing 2′ has guide surfaces 41′ adapted to guide the optical fiber32′ to the inner center of the housing 2′.

FIGS. 10A and 10B are a left side view and a plan view of the housing 2′of the optical receiving device 1′.

The optical fiber 32′ which has passed through a space defined by theguide surfaces 41′ of the housing 2′ further passes through a spacedefined by central guide surfaces 411′ into a position where it facesthe reflector 14′. Under the reflector 14′, four lenses 20′ are arrangedin a row along the width direction of the housing 2′ in the illustratedexample. This arrangement is advantageous in that flexibility and designfreedom can be increased when, for example, multiples of the opticalfiber 32′ are disposed between the guide surfaces 41′ or even if theposition of any one of optical fibers 32′ is somewhat misaligned becausethe light emitted from the optical fibers 32′ can be deflected by thereflector 14′ and directed to one of the lenses 20′.

The housing 2′ has a bottom 200′ formed with a first post 302′ and asecond post 303′ in predetermined positions forward and rearwardrespectively along the longitudinal center line thereof, which extenddownward toward the substrate. The first post 302′ and the second post303′ are circular columns protruding downward. In the example shown inFIG. 10A, in order to tolerate the error of optical alignment, the firstpost 302′ is a tapered column having its diameter gradually reduceddownward by minute degrees, and the second post 303′ is a straightcolumn having a constant diameter. The diameter of the first post 302′is larger than that of the second post 303′ in the vicinity of the topof the first post 302′, that is, adjacent to the bottom 200′. This meansthat with respect to the second post 303′, the diameter of the firstpost 302′ may be larger on its upper side of a reference point in thevertical direction and smaller on its lower side of the reference point.

FIG. 11 is a left side view illustrating that the housing 2′ is coupledto the substrate 10′.

The substrate 10′ is formed with a first reference hole 302 a′ and asecond reference hole 303 a′ for accommodating the first post 302′ andthe second post 303′ of the housing 2′. The first post 302′ and thesecond post 303′ are inserted into the first reference hole 302 a′ andthe second reference hole 303 a′, respectively. The first post 302′which is the tapered column is initially inserted in first referencehole 302 a′ with a minute clearance remaining therebetween. As theinsertion progresses gradually, the first post 302′ is fixed in aposition where it comes into contact with the first reference hole 302a′ without gaps.

As described later, the optical receiving device 1 of some embodimentshaving such coupling structure can minimize a misalignment that mayoccur in the process of assembling with the substrate 10′.

3. Method of Arranging Optical Receiving Device

The principle of the alignment method of the optical receiving device ofthe present disclosure will be described with reference to FIGS. 12A to12C which mainly show the plan view of the substrate 10.

With respect to the photodetector 12′ provided on the substrate 10′, thefirst reference hole 302 a′ and the second reference hole 303 a′ areformed in a line. The photodetector 12′, first reference hole 302 a′ andsecond reference hole 303 a′ respectively have center lines 111′, 112′and 113′ in the width direction (vertical direction in the drawing), andthe photodetector 12′, first reference hole 302 a′ and second referencehole 303 a′ have a longitudinal (horizontal direction in the drawing)center line as indicated by 114′. “K” is the gap between center line111′ and center line 112′, and “L” is the spacing between center line112′ and center line 113′.

In the small form factor optical transmitting device 1′ with a height ofless than 1 mm, correction of assembling tolerance means eliminatingerrors of several micrometers, so a sophisticated aligning operation isrequired. Typically, the substrate 10′ is completed and supplied inadvance according to specifications. The principal interest in theassembly of the substrate 10′ and the optical receiving device 1′ is thealignment of the lens 20′ with the least possible deviation with respectto the photodetector 12′ located on the substrate 10′. The idealassembly for this purpose provides a perfect alignment of the centers ofthe respective reference holes with the centers of the respective postsfree of deviation of even several μm. However, it is difficult to make acomplete intermeshing of members in the actual assembly process. Asolution to this problem is to minimize the error by having either oneof the first post 302′ and the second post 303′ fixed to eliminate thetolerance issue, and having the tolerance of the other post toexclusively affect the position of the lens 20′ to be aligned with thephotodetector 12′.

FIG. 12B is a diagram of the principle of the method where the firstpost 302′ is fixed immovably. It is assumed that K:L=1:8 and the secondpost 303′ is located deflected upward by 20 μm from the center of thesecond reference hole 303 a′. In this case, the first lens 20′ isdeviated from the photodetector 12′ downwardly by 2.5 μm by proportionalexpression.

FIG. 12C is a diagram of the principle of the method illustrating thesecond post 303′ is fixed immovably. It is assumed that K:L=1:8 and thefirst post 302′ is located deflected upward by 20 μm from the center ofthe first reference hole 302 a′. In this case, the lens 20′ is deviatedfrom the photodetector 12′ upwardly by 22.5 μm by proportionalexpression.

Therefore, when the photodetector 12′ is arranged outside of all thereference holes, fixing the first post 302′ in proximity to thephotodetector 12′ can eventually reduce the nine-fold error than whenthe second post 303′ is fixed. The above principle is applied not onlyto the case where the post deviates to the upward direction from thecenter of the reference hole but also to the case where the postdeviates in the downward or left/right direction.

Those skilled in the art will appreciate that assembly errors can beminimized as the proportional relationship of K:L increases, that is, asthe distance between posts increases or the first post is closer to thelight source or the first lens.

In order to fix the first post 302′ to the first reference hole 302 a′,the optical receiving device 1′ of some embodiments of the presentdisclosure has the first post 302′ designed as a tapered column so thatit is inserted into the first reference hole 302 a′ initially withminute degrees of clearance provided, and as the insertion graduallyprogresses, the first post 302′ is fixed at a position where it is incontact with the first reference hole 302 a′ without gaps.

The fixed position may be a point where the diameters of the first post302′ and the first reference hole 302 a′ coincide. However, since thepost is molded with, for example, a plastic material, it has a propertythat, when depressed, it is inserted by being compressed and deformed,and when pressure is released, returns to the original shape by elasticrestoring force. Therefore, the fixed position may be a position wherethe diameter of the first post 302′ is slightly larger than that of thefirst reference hole 302 a′, which is a margin for facilitating thefixation of the first post 302′.

From the above, one can see that it is desirable to design the firstpost 302′ as a tapered column having its diameter continuously varyincreasing from a range larger than the diameter of the first referencehole 302 a′ to a range smaller than the same.

Once the position of the first post 302′ is fixed, only the position ofthe second post 303′ affects the alignment of the light source and thelens, but the latter effect is very small compared to the effect on thelens by the deviation of either the first post 302′ or both posts 302′,303′ from the centers of all the reference holes. Therefore, it becomespossible to restrict the alignment error of the light source and thelens to within a few micrometres to achieve the sub-miniaturizationthereof.

Although exemplary embodiments of the present disclosure have beendescribed for illustrative purposes, those skilled in the art willappreciate that various modifications, additions and substitutions arepossible, without departing from the idea and scope of the claimedinvention. The scope of the technical idea of the present embodiments isnot limited by particular illustrations. Accordingly, one of ordinaryskill would understand the scope of the claimed invention is not to belimited by the explicitly described above embodiments but by the claimsand equivalents thereof.

1. An optical transmitting device, comprising: a first lens configuredto collimate a light from a light source; a reflector disposed above andin alignment with the first lens and configured to reflect thecollimated light from the first lens; a second lens disposed on a sideof and in alignment with the reflector and configured to transmit thereflected light to an optical fiber; and a housing configured to housethe first lens, the second lens, and the reflector, wherein the housinghas a divided structure composed of a body at a lower position and acover at an upper position, and the housing has a height less than 1 mm.2. The optical transmitting device of claim 1, wherein the body isconfigured to mount the first lens and the reflector, and the cover isconfigured to mount the second lens.
 3. The optical transmitting deviceof claim 1, wherein the cover is formed with a hole for injecting epoxyresin or refractive index matching oil.
 4. The optical transmittingdevice of claim 1, wherein the first lens is a collimating lens and thesecond lens is a focusing lens.
 5. The optical transmitting device ofclaim 2, wherein the body comprises: a reflector mount configured tomount the reflector; and a first lens mount configured to mount thefirst lens.
 6. The optical transmitting device of claim 5, wherein thereflector mount stands vertically from a bottom of the body, and thefirst lens mount is spaced apart from the reflector mount by apredetermined distance and is formed in front of the reflector mount,extending from the bottom upward and then forward laterally.
 7. Theoptical transmitting device of claim 6, wherein the first lens isinstalled on an upper surface of the first lens mount with a convexsurface of the first lens facing downward, and the reflector isobliquely installed across an end of the upper surface and an apex ofthe reflector mount.
 8. The optical transmitting device of claim 2,wherein the cover comprises a second lens mount configured to mount thesecond lens.
 9. The optical transmitting device of claim 8, wherein thesecond lens mount extends vertically downward from an upper surface ofthe cover, and the second lens is installed on a front surface of thesecond lens mount.
 10. The optical transmitting device of claim 7,wherein the body comprises a left body side coupling portion and a rightbody side coupling portion, each extending from forwardly of the bottomto near a middle region of the body, the left body side coupling portionand the right body side coupling portion being symmetrical in structure,and respectively including one or more flaps, one or more receivingholes and one or more latch members; wherein the flaps extend verticallyupward from the bottom to provide a protective frame for protecting atleast the first lens and the reflector laterally from the outside; andwherein the bottom has an open space behind the left body side couplingportion and the right body side coupling portion, which cooperates withthe cover so as to provide a space through which an optical fiberpasses.
 11. The optical transmitting device of claim 10, wherein thecover includes an upper side formed with a left cover side couplingportion and a right cover side coupling portion corresponding to theleft body side coupling portion and the right body side couplingportion, the left cover side coupling portion and the right cover sidecoupling portion being symmetrical in structure, and respectivelyincluding one or more flaps, one or more receiving holes and one or morelatch members.
 12. The optical transmitting device of claim 1, whereinthe housing comprises a first post and a second post installed extendingdownward at predetermined front and rear positions in the bottom,respectively.
 13. The optical transmitting device of claim 12, whereinthe first post and the second post are circular columns.
 14. The opticaltransmitting device of claim 13, wherein the first post is a taperedcolumn whose diameter decreases gradually downward by minute degrees,and the second post is a straight column having a constant diameter. 15.The optical transmitting device of claim 14, wherein the first post hasthe diameter larger than that of the second post near the bottom of thebody.
 16. The optical transmitting device of claim 1, wherein the secondlens is installed at a predetermined position to fully accommodate thereflected light.